According to current estimates, more than 8000 man-made satellite objects are orbiting the earth. Tracking and identifying any particular one of these satellite objects from earth can present certain challenges, and typically requires a powerful telescope and illumination of the object by the sun. However, optimal solar illumination conditions usually occur in a limited time window near sunrise and sunset. Passively tracking satellites at night can pose additional challenges, and typically requires sophisticated infrared detectors and optics that are optimized for the infrared spectrum. Passively tracking satellites during the day is extremely difficult, if not impossible, due to background radiation.
Some satellites are very small and are even more difficult to identify and track. Satellite identification can also be problematic when there is more than one object in the field of view of a tracking telescope. Orbital parameters can be utilized to predict the orbit of a satellite; however, small errors in the orbital parameters can lead to an incorrect identification of a satellite. Imaging the target satellite is another method of identification, but this method is highly dependent upon the orientation of the satellite relative to the observer's view. In general, there is a very narrow window in which a satellite can be identified and passively tracked.